So basically, everything is known good except for the PCM? I'm with Master Tech on this one, time for a scan tool.

 

with the car running, unplug the Coolant temp sensor. It should throw the PCM into default mode and command the fan ON. if that doesnt work, then I am with Master Tech on this one.

 

I have a 2005 Grand Caravan. the check engine light came on. I scanned it and found the Fan Circuit 1 fault. # P0480. I checked under the hood and found the power plug to the fan on the driver's side of the rad unplugged. I plugged it in and cleared the code. the next day it was back. Checking further i found the relay for the fan (Behind the grille). I checked the fuse which was good. I unplugged the coolant temp sensor. and the fans do not come on. I unplugged the the relay and jumped the contacts in the plug and both fans came on. When the relay is plugged in nothing works. I performed some tests and found there is no signal coming from the ECU. Any suggestions?

 

Pretty common for the relay to crap out. It is held on with a rivet so get one of those as well if you replace it.

 

I have the same issue, no ground coming from pcm to signal fan relay, harness between the two is good, unplugged the coolant temp sensor and the fans come on, would that point to just a bad coolant temp sensor?